Formula Writing of Organic Compounds - PowerPoint by whn12745

VIEWS: 643 PAGES: 45

More Info
									Chapter 3 - Molecules,
  Compounds, and
 Chemical Equations




                         1
In this chapter we will build on your understanding of
compounds.

       •   forces of attraction within compounds
                - chemical bonds

       •   representing and naming compounds
                - types of chemical formulas
                - chemical nomenclature

       •   quantitative aspects of compounds
               - percent composition
               - using experimental data to determine chemical
                   formulas

       •   representing how compounds change and react
                - chemical equations                       2
2 H2 (g) + O2 (g) → 2 H2O (l)


                                3
I. Chemical Bonds

•The overwhelming majority of elements
occur in chemical combination with other elements.


•Why are most atoms found bonded to other
atoms in the form of chemical compounds?


•   What causes compound formation?

                                               4
A.Ionic Bonds

  1. Ionic bonds are usually between a
     metal and a non-metal.

  2. How does an ionic bond form?
  Video – Reaction of Na (s) + Cl2 (g)
  http://www.youtube.com/watch?v=Ftw7a5ccubs


  3. Ionic compounds are not composed
  of molecules.


                                               5
B. Covalent Bonds

     1. Usually between two non-metal atoms.



     2. How does a covalent bond form?




                                               6
 In which of the following arrangements is the
 negative charge most stabilized?


A.                     B.                C.




                                                 7
3. The fundamental repeating
unit of covalently bonded substances is the
molecule.

     a. Representing molecules

           1. ball and stick model

           2. space - filling model




                                              8
Ball and Stick Model of Caffeine




                                   9
Space Filling Model of Caffeine




                                  10
3. Molecular Formula


4. Structural Formula


5. Empirical Formulas




                        11
12
D. Some substances contain ionic
and covalent bonds.

For example, CaCO3




                                   13
14
C. Attractive forces between molecules
are not chemical bonds.




                                         15
6) What is the empirical formula for C4H10O2?

A) C2H5O

B) CHO

C) C2H4O

D) CHO2

E) CH2O

                                                16
 Which of the following contains BOTH
ionic and covalent bonds?

A) CaI2

B) COS

C) NH4Cl

D) SF6

E) None of the above contain both ionic
and covalent bonds.
                                          17
II. Nomenclature and Formula
Writing – Ionic Compounds

 A. Formula Writing – Ionic Compounds

    1. Positive ion is written first
    2. Sum of charges should equal zero.
    3. Formulas for ionic compounds contain the
          lowest ratio of ions.
    4. Use parentheses when indicating more than
          one polyatomic ion.

                                              18
5. Formula Writing – Examples

K+        S2-

NH4+      SO4 2-


Fe 3+     SO3 2-

Pb 4+     O 2-


                                19
B. Nomenclature – Ionic Compounds

      1. Cation read first.

      2. Anion read second.
             • monoatomic anions - end in “ide”
             • polyatomic “oxyanions” –
                        end in “ate” and “ite”
      3. Practice

FeP               Cu2Cr2O7        Hg2Cl2


                                                  20
C. Hydrates
     1. A hydrate is an ionic compound with
a specific number of water molecules
associated with each formula unit.

     2. Water can be driven off by heating.




                                              21
III. Nomenclature and Formula
Writing – Molecular Compounds

 A. Binary molecular compounds

           CO    vs CO2
   1. All end in “ide”.
   2. Use Latin numerical prefixes to indicate
          the numbers of each type of atom.
   3. Drop “mono” from first element if mono
          is used.
                                                 22
B. Organic Compounds

    1. Organic compounds are carbon-based.
    (C,H, and O,N,S, X)

    2. Organic compounds include
    biomolecules, pharmaceuticals, plastics,
    textiles, DNA, etc.

    3. Simple hydrocarbons – Alkanes

    4. Structural features called functional
    groups are the basis for classifying organic
    compounds                                 23
24
25
Organic vs. Inorganic Compounds




                                  26
IV. Acids – Nomenclature
and Formula Writing

   A. Binary Acids ( H+ + one other element)



   B. Oxyacids (H+ + oxyanion)



                                           27
Which of the compounds C4H10, BaCl2,
Ni(NO3)2, SF6 are expected to exist as molecules?

A) only C4H10

B) C4H10 and SF6

C) C4H10, Ni(NO3)2, and SF6

D) BaCl2 and Ni(NO3)2


                                                28
What is the charge on the Cr ions in Cr2O3?

A) 2-

B) 1+

C) 2+

D) 3+



                                              29
Identify a hydrocarbon.

A) CH3CH2OCH2CH3

B) CH3CH2OH

C) CH3CH2NH2

D) CH3CH2CH2CH3

E) CH3COOH

                          30
Determine which formula/ name pair below is
correct.


A. P2O5, phosphorus pentoxide

B. H2O, dihydrogen monoxide

C. NaNO3, monosodium nitrate

D. K2O, dipotassium monoxide

E. Fe2O3, iron(II) oxide                      31
V. Mass of Molecules
   A. Mass of one molecule = formula mass
        (amu)



   B. Molar mass – mass of one mole of
   molecules (grams)




                                            32
VII. % Composition of Compounds

      A. % composition of the elements
in a compound can be determined from the
chemical formula.
      Example: Ammonium nitrate is commonly
     used as a fertilizer. Calculate the mass % N in
     ammonium nitrate.

B. % composition can be used as a conversion
     factor.
     Example: How much ammonium nitrate is
     needed to provide 1.00 lb of N?
                                                       33
Example: Foodservice salt packets contain 0.50
g NaCl. Most Americans consume 3436 mg of
sodium a day (more than twice the 1500 mg
recommended maximum!). How many salt
packets contain 3436 mg of sodium? NaCl is
39.0 % Na by mass.




                                                 34
VII. Conversion Factors in
Chemical Formulas

      A. Conversion formulas can be constructed
from chemical formulas.



        B. Example: How many g of nitrogen are in
5.00 lb of ammonium sulfate (another common
fertilizer)?

                                                    35
VIII. Empirical and Molecular
 Formulas from Experimental
 Data
A.The mole ratios of elements in a compound
can be determined from elemental analysis.

Example: Elemental analysis of a 15.0 g
unknown sample gave the following results:
     2.82 g Na, 4.35 g Cl, 7.83 g O
Use the data above to determine the empirical
formula of the compound.
                                                36
Example: Benzo[a]pyrene is a carcinogen found
in coal dust, cigarette smoke,and charcoal
grilled meats. Elemental analysis gave the
following results.

  95.21 % C
  4.79 % H

1. Determine the empirical formula
   for benzo[a]pyrene.

2. If the molar mass of benzo[a]pyrene is
252.30 g/mol, what is the molecular formula?
                                                37
B. Combustion Analysis of a Compound

     1. What is combustion?

     2. Combustion analysis is used to determine
     the empirical formula of a compound.




                                               38
3. Examples

     a. Combustion analysis of a hydrocarbon
produced 33.01 g CO2 and 13.51 g H2O.
Calculate the empirical formula for the
hydrocarbon.


What is the molecular formula given the molar
mass of the hydrocarbon is 42.09?



                                                39
b. Vitamin C (MM = 176.12 g/mol) is a compound
of C, H, and O found in many natural sources,
especially citrus fruits. When a 1.000 g sample
of vitamin C is placed in a combustion chamber
and burned, the following data are collected.
            1.50 g CO2
            0.41 g H2O
Use the data above to determine the empirical
formula and molecular formula for vitamin C.




                                                  40
IX. Chemical Equations

   A. Chemical equations summarize
   chemical changes.

   B. Characteristics of a chemical equation
   to know
         • chemical formulas
         • reactants and products
         • state symbols
         • coefficients
         • balanced equation
                                               41
c. Practice

1. When aluminum metal reacts with air, it produces
a white, powdery compound, aluminum oxide.

2. Gaseous carbon monoxide reacts with
hydrogen gas to form gaseous methane and
liquid water.

3. Write the reaction for the complete combustion
of pentane.


                                                    42
What are the coefficients for the decomposition of
nitroglycerin?

__ C3H5N3O9  __ N2 + __ CO2 + __ H2O + __ O2
 A. 2,3,6,2,1
 B. 2,3,6,5,1
 C. 4,6,12,10,12
 D. 4,3,12,10,1
 E. 4,6,12,10,1




                                                     43
Calculate the number of carbon atoms in 25.0
grams of isopropyl alcohol (C3H8O).



A) 1.25 C atoms
B) 15.0 C atoms
C) 2.51 x 1023 C atoms
D) 7.52 x 1023 C atoms
D) 2.07 x 10–24 C atoms



                                               44
An unknown compound contains the following
percents by mass: C: 60.86%, H: 5.83%, O:
23.16%, and N: 10.14%. Find the empirical
formula.
A) C6H8O2N2
B) C7H8O2N
C) C6H8O2N
D) C8H8O2N
E) C8H8ON



                                             45

								
To top